Bibliographic details of the publications referred to by author in this specification are collected at the end of the description.
Reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that this prior art forms part of the common general knowledge in Australia or any other country.
The study of plant embryogenesis has been regarded as fundamental to understanding plant development. It is during embryogenesis that meristems and basic plant tissue systems are established. Basically, embryogenesis involves two main processes: the induction of embryogenic potential and the expression of the embryogenesis programme. Because of the totipotency of the plant cells, each cell has the capability to become embryogenic and to develop into a whole plant.
Recent advances in micropropagation and manipulation of tissue culture conditions has led to the possibility of multiplying vegetatively many plant species efficiently and rapidly in vitro. For many commercial production systems, conventional plant breeding and seed production methods are slow and therefore limit the ability to realize the maximum potential of selected genotypes. However, the development of economically-viable propagation systems necessitates the existence of efficient methods of embryo- or organogenesis. Such methods have been generated for many, but not all species.
There are very high demands for oil-palm. Accordingly, a major area of study in the oil-palm industry seeks to find improved ways to increase oil yield. With the ability to maintain uniformity of planting materials in tissue culture, improvements in yield of up to 20% may be able to be realized. In the case of oil-palm, however, little is known about the biology of somatic embryogenesis despite the economic importance of the crop and work to date has resulted in average rates of in vitro embryogenesis of only 6% (Wooi, 1995). Such low rates are inconsistent with an economically viable system.
Most of the earlier studies concentrated on the development of methodologies for the initiation and production of somatic embryos (Jones, 1974; Ahee et al., 1981; Pannetier et al., 1981). These groups worked mainly on the manipulation of phytohormones in the media as well as on introducing tissues with better clonability to further improve the process. Schwendiman and colleagues (1988) carried out histological analysis of somatic embryogenesis from leaf-derived callus, detailing the emergence of callus and the subsequent formation of somatic embryos, with shoot and root apices. Not long before that, Turnham and Northcote (1982) investigated the occurrence of biochemical indicators that are useful in the prediction of embryogenic potential.
More recently, the importance of understanding molecular switches, that occur in somatic cells and induce them to become embryogenic, has been highlighted (Dudits et al., 1995).
In this regard, the rapid introduction of and improvements in recombinant DNA technologies has greatly facilitated the study of plant development and provided researchers with sophisticated precision tools for investigating underlying molecular mechanisms.
There is a need to develop an effective and efficient method for the production of somatic embryos and new approaches to be brought to bear in attempts to realize that end.
In work leading up to the present invention, the inventors sought to identify underlying factors involved in the induction of embryogenesis. In so doing the inventors located and isolated a polynucleotide sequence which was surprisingly found to be expressed only in zygotic embryo and embryogenic callus. The polynucleotide sequence or an amino acid encoded thereby of the present invention is useful inter alia as a means of discriminating embryogenic from non-embryogenic material. The molecular marker represents a member of a new class of molecules from monocot plants such as but not limited to oil-palm and related plants.